1. Field of the Invention.
This invention relates to solid fuels for use in rocket ramjet applications.
2. Description of the Prior Art.
Ramjet engines which utilize solid fuels are known. In such engines a combustion chamber is lined with the solid fuel, air is used as the oxidizer and the fuel is combusted to propel the engine. Such engines are often volume limited. That is, while weight may be a consideration in engine design, volume is usually the subject of more critical consideration.
In considering what fuel one wishes to use in a volume limited situation, one must consider the density of the fuel. The fuel should have a relatively high density.
In considering what fuel to use in a volume limited situation, one must consider the heat of combustion per unit volume of the fuel. The fuel should have a high volumetric heat of combustion.
And finally, in considering what fuel to use in a volume limited situation, one must consider the actual performance obtained when unit volume of fuel is burned. No matter what the theoretical volumetric heat of combustion is, the fuel is simply not useful as such unless good combustion efficiency is obtained. That is, a fuel with a high theoretical volumetric heat combustion may be less useful than one with a relatively lower volumetric heat of combustion if the one with the lower value burns more efficiently. Combustion efficiency can only be determined by actual experimentation. That is, one cannot predict, with absolute certainty, that a fuel will burn efficiently by simply knowing the properties of the fuel. Combustion efficiency depends, to a large extent, on stay time which, in volume limited situations, is naturally of short duration. And, of course, combustion efficiency depends on ignition temperature. If a fuel will not ignite at temperatures produced within the combustion chamber, it simply isn't useful in that particular combustion chamber.
At the present time, hydroxy terminated polybutadiene alone is the most predominantly used solid ramjet fuel. While hydroxy terminated polybutadiene works admirably well, it would be desirable to have ramjet fuels which had higher densities, higher theoretical volumetric heats of combustion and which burned as efficiently or more efficiently than hydroxy terminated polybutadiene. It is, accordingly, the primary object of this invention to provide such fuels.